The cost to mail a package is $5 for the first 2 pounds and 40 cents for each additional ounce.

Which of the following functions represents the cost to mail a package if x is the number of ounces over 2 pounds?

f(x) = 0.4(x + 2)
f(x) = 10 + 0.4x
f(x) = 5 + 0.4x